Conventional means of power production from combustion of a fuel typically lack the ability to simultaneously achieve both high efficiency power generation and carbon capture. This limitation is magnified when using solid fuels in the combustion reaction because of the solid and inert nitrogen gas contents remaining in the combustion product stream. Accordingly, there is an ever growing need in the art for systems and methods for high efficiency power generation allowing for a reduction in CO2 emission and/or improved ease of sequestration of produced carbon dioxide.
One publication in the field of high efficiency power generation with carbon capture, U.S. Pat. No. 8,596,075 to Allam et al., provides one solution whereby a solid fuel such as coal, lignite, pet-coke or biomass is gasified by reaction with oxygen and optionally steam in a partial oxidation reactor operating at a sufficiently high pressure and temperature to allow substantially complete conversion of the solid fuel to a gaseous fuel comprising mainly carbon monoxide and hydrogen as the combustible components together with combustion derived impurities, such as H2S, CS2, carbonyl sulfide (COS), HCN, and NH3. The partially oxidized net product gas is cooled, ash is separated, and it is optionally compressed to allow it to be introduced as fuel into the combustion chamber of the power generation system. The operating pressure of the partial oxidation system and the power generation system can be such that no compression of the fuel gas is required. The power generation system combustor operates with an excess of O2 present following combustion, which ensures that the fuel and combustion derived impurities are converted from the reduced state to their oxidized forms comprising predominantly SO2 and NO. The partial oxidation reactor can be provided with transpirationally cooled walls with a high pressure recycle CO2 stream cooling the partial oxidation product gas before ash removal at a temperature level of about 800° C. Further cooling of the partial oxidation gas to about 400° C. is necessary to ensure that all fine ash particles together with solidified volatile inorganic components are condensed and filtered to prevent solid deposition, corrosion, and blockage of down-stream equipment. The cooling of the partial oxidation gas from 800° C. to 400° C. must take place in a heat exchanger with tubes for the high pressure partial oxidation gas that are resistant to metal dusting corrosion due to the Boudouard carbon forming reaction and the high CO partial pressure in the partial oxidation gas. This is shown below in Formula (1).CO+CO═C+CO2  (1)The tubes must be designed to allow periodic water washing to remove solid deposits derived from the condensation of volatile inorganic components present in solid fuels, particularly coal and lignite.
Despite the advances of the above-described publication, the systems and methods described therein still do not provide a most advantageous solution to the problems arising when using solid fuels as a power production combustion fuel. Thus, there remains a need for further systems and methods for high efficiency combustion of solid fuels with carbon capture.